In many fuel supply systems applicable to internal combustion engines, fuel injectors are used to inject fuel pulses into the engine combustion chamber. A commonly used injector is a closed-nozzle injector which includes a nozzle assembly having a spring-biased nozzle valve element positioned to control a flow of high pressure fuel into the cylinder. The nozzle valve element also functions to provide a deliberate, abrupt end to fuel injection, thereby preventing a secondary injection which causes unburned hydrocarbons in the exhaust. The nozzle valve element is positioned in the injector cavity and biased, for example, by a bias spring, so that when an actuation force exceeds the biasing forces acting on the element, the nozzle valve element moves to allow fuel to pass into the combustion chamber, thus marking the beginning of the injection event.
Internal combustion engine designers have increasingly come to realize that substantially improved fuel supply systems are required in order to meet the ever increasing governmental and regulatory requirements of emissions abatement and increased fuel economy. Therefore, such designers are continually searching for ways to improve control over fuel injection to help meet the economically and governmentally mandated demands for increasing fuel economy and reduced air pollution.